790 CYST. 



become irritated and inflamed, and these tunics, brane is detached and enjoys an independent 

 at first characterised by so much tenuity, may, life; the false membrane acquires a vitality 

 by the pure and simple effect of their rapid rivalling that, of normal tissues, 

 development, or as a consequence of their We believe, therefore, that a cyst may be 

 relation with very moveable organs, or by the developed, which, as far as general appearances 

 effect of accident, to which they are exposed, are concerned, shall be analogous to the ace- 

 become susceptible of almost unlimited trans- phalocysts, wanting, however, the one great 

 formation. attribute, independent existence, and having 



We believe, therefore, that all the varieties a vascular communication with the tissue upon 



composing this class owe their existence to which it is developed : are not those cysts 



irritation ; in the synovial the irritation is spe- which are often seen upon the cortical sub- 



cific and caused by pressure, in the serous, stance of the kidney, and upon other organs; 



we believe it to be of another kind, in many of this class or character ? 



of them it is similar to that which presides Dr. Hodgkin* has inferred that those cysts 



over the development of hydatids : the only which are so often found on the surface of the 



difference between certain of them, those, for kidneys owe their existence to the obstruction 



instance, which are so nearly isolated, having of an excretory canal ; others have believed 



merely a vascular communication, and an that this fact was demonstrated, because it was 



hydatid, is perhaps simply, that their existence said that their contents had the odour of urine, 



has not been sufficiently prolonged to permit Without denying this position, I may state 



with safety the rupture of this umbilical cord, that the smell of serum and that of limpid 



if I may so term it, by which they are con- urine are not very dissimilar. If they were a 



nected to the surrounding tissues. We must consequence of the obstruction of an urinary 



now endeavour to explain the circumstances duct, it is evident, from the size they some- 



* under which these cysts are developed. times attain, that secretion has proceeded after 



The experiments and observations of Cru- the obstruction has been developed ; why then 



veilhier shew, in the most convincing manner, does it not go further ? why do they not attain 



that humidity, abundance, and the bad or ve- considerable magnitude ? 



getable quality of the nourishment of an In the earlier periods of their existence the 

 animal, are unequivocal means of producing organisation of these bodies is simple, but in 

 acephalocysts. If by the concurrence of these their progress they may experience many mo- 

 circumstances acephalocysts may be produced, difications. Their internal and external sur- 

 it must be evident that by the agency of the faces are essentially different; the internal is 

 same causes a modification of existing tissues, usually smooth and polished like serous mem- 

 irritation, in fact, of a specific kind, has been branes ; sometimes it is soft, flocculent, and 

 excited by which a state favourable to their easily detached : the external is in contact with 

 development has been produced. Admitting cellular tissue, and partakes more or less of its 

 then that by such means a particular kind of character, but frequently it acquires a density 

 irritation may be set up in certain tissues, we which distinctly separates it from the surround- 

 must go further ; that irritation must be suf- ing tissue. There is scarcely any form of trans- 

 ficient to cause the exhalation of a particle of formation which may not occur in these organs. 

 lymph, that lymph, as in the case of a pseudo- The internal surface occasionally acquires a 

 membrane, becomes organised, acquires step very complicated organisation ; it may be co- 

 by step an individual existence, it will be the vered with hair proceeding from follicles de- 

 minimum of organisation and independent veloped in its parietes, and it may present 

 vitality, but still, when its separation is achieved, other anomalies. The external surface may 

 it will be a living being. Supposing this idea acquire a very considerable density, and may 

 to be correct, it may follow that a variety of present something like a fibrous appearance, 

 modifications of such products, more or less but upon further investigation we find that it 

 independent, may be in a similar manner pro- does not possess any fibre, neither does its 

 duced. texture offer any linear or radiated arrange- 



It is certainly difficult to reconcile the mind ment. When once organised, the tunic which 

 to the idea that the process of irritation or of constitutes the cyst enjoys all the attributes 

 inflammation can, under any circumstance, of living tissues, and is susceptible of similar 

 excite the development of an animal possess- morbid modifications. It may become in- 

 ing to a certain extent an independent ex- flamed, it may degenerate into a cartilaginous 

 istence, but this is not more difficult than to state, may become incrusted with phosphate 

 conceive that molecules of a plastic living of lime, converted into erectile tissue, may 

 substance may form organic membranes, and become scirrhous, and so on ; and the ex- 

 yet this is demonstrable. halation or secretion may be so changed that 



This has been clearly shewn in the article cysts of similar origin may contain the most 



ADHESION; in fact, the more we study the dissimilar products, 

 phenomena of organisation, the more we are 



impelled to admit a proper vitality in certain BIBLIOGRAPHY. Cruveilhier, Essai sur 1'Anat. 



products of living bodies. The analogy which Path - t - P- 202 & * e< l- Gendrin, Hist. Anat. 



exists between false membranes and hydatid i e h s ST '' ?' ' f Be9in> " 



j^.i Chir. Path. art. Kyste. 



sacs appears to be especially calculated to (ft Phillips ) 



elucidate this subject. But whilst the false 



membrane remains in vital communication with 



the individual, the acephalocystic false mem- * Med. Chir. Transact, vol. xv. part 2. p. 270. 



